#!/usr/bin/perl

# http://perlmonks.org/?node_id=1133857

use warnings;
use strict;

print zip("ABCDEFGHIJ", "abcde"), "\n";

sub zip
  {
  my ($str1, $str2) = @_;
  my $gap = length($str1) - 1;
  my $len2 = length $str2;

  join '', grep defined, "$str1$str2" =~ /(.)(?=.{$gap}(.)|.{$len2})/gs;
  }